I still feed my 19 month old to sleep 🤷 Honestly it's just going to be hard. No two ways about it. Drop feeds very slowly. When you stop you may get hit by big sad feels so be prepared. Its hormonal!
Could you try expressing some breast milk and giving in a bottle initially? Then once he's used to that switch to a mix of breast milk and formula until you can just give formula. My breast fed baby will take breast milk from a bottle (me feeding her) no problem but often puts up more fight over formula
Feeding to sleep is what nature intended! We still feed to sleep at 15 months with no intentions of stopping. Baby likely won’t accept a bottle from you/ with you around without some protest and upset as they want to nurse and know you have milk. Consistency will be key but if you’re wanting to wean you’ll need to accept it’ll cause upset and support your little one through their feelings and meet their needs for connection in other ways x